How cheap is cheaper you ask.
Well when the parvalux that I had died, I enquired about a replacement, Parvalux quoted me £280, The motor from Hemingway Kits is around the £60 mark and is excellent quality, Fractional hp motors can easily be found for less than £80 so why do parvalux command such a high price (I ask the same question about Myford lathes!!)
I wouldn't bother with the cheapo grinder motors, having looked at these as a possible alternative, I discounted them as most of them are not reversible, or run horribly when reversed, they have poor quality bearings, badly of totally unbalanced rotors and vibrate like a anne summers party piece. (There's a reason they are £25
)